giraffes feed on the leaves of trees and other plants in areas of Africa . Both Lamrack and Darwin explained the evolution of long necks in terms of getting leaves from tall trees . Neither scientists used any evidence to support their theory . Recently scientists , have tried to explain how the long neck of the giraffe might have evolved . These are some of their observations
Giraffes spend almost all of the dry season , when food is scarce , feeding on low bushes
Only in the wet season do they feed from tall trees when new leaves are plentiful
Females spend over 50% of their time feeding with their necks horizontal . Both sexes feed faster and most often with their necks bent
Long giraffe necks are very important in male-to-male combat . Males fight each other with their long , powerful necks
Females prefer male giraffes with longer necks
do the observations support or reject the explaination that the long necked giraffe evolved to get leaves from tall trees ? (2)

reject because

giraffes spend almost all of the dry season feeding on low

bushes

both sexes feed faster and most ofetn with their necks bent

giraffes feed on the leaves of trees and other plants in areas of Africa . Both Lamrack and Darwin explained the evolution of long necks in terms of getting leaves from tall trees . Neither scientists used any evidence to support their theory . Recently scientists , have tried to explain how the long neck of the giraffe might have evolved . These are some of their observations Giraffes spend almost all of the dry season , when food is scarce , feeding on low bushes Only in the wet season do they feed from tall trees when new leaves are plentiful Females spend over 50% of their time feeding with their necks horizontal . Both sexes feed faster and most often with their necks bentLong giraffe necks are very important in male-to-male combat . Males fight each other with their long , powerful necks Females prefer male giraffes with longer necks
give another explaination for the evolution of the long neck (2)

mutations produce male giraffes with longer necks

females are more likely to mate with long necked male giraffes their genes are more likely to pass onto the next generation

there are tow forms of peppered moth , the pale form and the dark form . In an investigation , pale and dark moths were placed in different positions on trees in two woods . One wood was in an industrial area where the bark was blackened by pollution . The other wood was unpolluted , and the tree bark was covered in pale mosses and lichen . After three days , the surviving moths were counted . The results are shown in the table
what can you tell from these results about the survival of the two types of moth in polluted and unpolluted woods , and in different positions of the tree ? (3)

the pale moth survives best in unpolluted areas

the dark moth survives best in polluted areas

% survival on the underside of branches is greater in both situations

here are tow forms of peppered moth , the pale form and the dark form . In an investigation , pale and dark moths were placed in different positions on trees in two woods . One wood was in an industrial area where the bark was blackened by pollution . The other wood was unpolluted , and the tree bark was covered in pale mosses and lichen . After three days , the surviving moths were counted . The results are shown in the table
explain how the resultsprovide evidence for one theory of evolution (3)

different sorts of moths

ideal of differntial survival in different habitats

evidence for natural selection

daphina are microscopic water fleas . Midge larvae prey on Daphina . The midge larvae release a hormone into the water . Daphina respond to these hormones by growing larger protective "hemlmet"- like structures . Scientist were suprised to observe that the offspring of Daphinia females who had been exposed to these hormones always had larger helmets than offspring whose mothers had never been exposed to the hormones . The offspring with the large helemets went on to produce offspring with large helmets . Explain why the scientists' observations seem to contradict the theory of natural selection (2)

this indicates inheritance of aquired characteristics

superbug may hit the price of coffee
the coffee bean borer , a pest of the coffee crop , can be controlled by the pesticide endosulphan . However strains of the insect that are up to 100 times more resistant to the pesticide have emerged on the south Pacific island of New Caledonia . For full resistance to be passed on to an offspring two copies of the new resistant allele should be inherited , one from each parent . There is much inbreeding with brother-sisters mating happening in every generation , so it takes only a few generations before all the descendants of a single resistant female have inhertied two copies of the resistant allele . If this resistance spreads from New Caledonia , it will mean the loss of a major control method . This will present a serious threat to the international coffee industry
suggest how the the allele for the resistance to endosulfan may have arisen (1)

mutation

superbug may hit the price of coffee the coffee bean borer , a pest of the coffee crop , can be controlled by the pesticide endosulphan . However strains of the insect that are up to 100 times more resistant to the pesticide have emerged on the south Pacific island of New Caledonia . For full resistance to be passed on to an offspring two copies of the new resistant allele should be inherited , one from each parent . There is much inbreeding with brother-sisters mating happening in every generation , so it takes only a few generations before all the descendants of a single resistant female have inhertied two copies of the resistant allele . If this resistance spreads from New Caledonia , it will mean the loss of a major control method . This will present a serious threat to the international coffee industry
how would you expect the proportion of normal coffee bean borers on New Caledonia to change over the next few years (3)

fall

the resistant beetles more likely to survive to breed , their offspring more likelt to appear in next generation

superbug may hit the price of coffee the coffee bean borer , a pest of the coffee crop , can be controlled by the pesticide endosulphan . However strains of the insect that are up to 100 times more resistant to the pesticide have emerged on the south Pacific island of New Caledonia . For full resistance to be passed on to an offspring two copies of the new resistant allele should be inherited , one from each parent . There is much inbreeding with brother-sisters mating happening in every generation , so it takes only a few generations before all the descendants of a single resistant female have inhertied two copies of the resistant allele . If this resistance spreads from New Caledonia , it will mean the loss of a major control method . This will present a serious threat to the international coffee industry
explain why "it takes only a few generations before all the descendants of a single resistant female inherited two copies of the resistance allele (3)

inbreeding between resistant brothers and sister , will produce some individuals with 2 copies of the resistant allele , if two of these individuals breed their offspring will be resistant

cane toads were first introduced into Austrialia in 1935 . The toads contain toxins and most species of Austrialian snake die after eating the toad
the cane toad toxin does not affect all snakes the same way . Longer snakes are less affected by toad toxin
Scientists investigated how red bellied black snakes had changed in the 70 years scince cane toads were introduced into their area . They found that red bellied black snakes had become longer by about 3-5%
suggest an explianation for the change in the body length of the red bellied black snakes since the introduction of the cane toads (4)

mutation

produces longer snake length

longer snake survives

survivors reproduce

gene passed to next generation

much of the evidence for the evolution of humans comes from fossils . Explain why this fossil evidence is often too dificult to interpret (2)

explain , as fully as you can , what eventually happens to energy from the sun which is captured by plants in the wood (10)

energy stored in cells/tissues/growth passed up food chain

less energy is stored at each feeding level

because only part of energy taken in used for growth

some used for repair

some used in main body systems

some lost in respiration

some converted into different forms of energy e.g. movement or heat

detritus feeders digest the remains

a student grew a plant in an upright pot . She then put the pot in a horizonatl position and left the plant in the dark for two days . After 2 days the shoot of the plant began to bend upwards
explain fully why the plant responded in this way (4)

stem is negatively geotropic

gravity causes the redistribution of auxin to lower side of the stem

the auxins causes the cells on the lower side to grow faster

so the stem grows upwards

explain how a population of antibiotic resistsant bacteria might develop from non-resistant bacteria (3)

variation/mutation of bacteria

leading to resistant bacteria surviving

and then resistant bacteria breed

suggest two reasons why it is an advantage to keep farm animals disease free (2)

the treated animals do not use energy in overcoming their illness

animals do not infect other animals/farm workers

why was darwins theory only gradually accepted

it went agaisnt religious beliefs

there was onlu little evidence

the carbon in dead plants is returned to the atmosphere via the carbon cycle describe this part of the carbon cycle (4)

decomposers and detritus feeders

decay the bean plant

repsiration of the descomposers and detritus feeders

releases carbon dioxide

in 2006 blue-moon butterflies almost became extinct
Wolbachia bacteria killed males before they could hatch from eggs . Only females were resistant to bacteria . In 2006 the number of male blue-moon butterflies had decreased to only 1% of the population . 2 years later , the number of males was equal to the number of males . Scientists believe that a change in a gene suddenly occured to make some males resistant to bacteria . The number of male blue-moon butterflies increased quickly after the new form of the gene had appeared
suggest why (4)

because the males had a mutation which meant that they were resistant to Wolbachia , so they were better adapted to their environment , so surivived to reproduce and passed on the gene that allowed them to be resistant to Wolbachia to the next generation

diet and inherited factors affect the level of cholestrol in a persons blood . Too much cholestrol may cause deposits of fat to build up in blood vessels and reduce the flow of blood . This may cause the person to have a heart attack Some drugs can lower the cholestrol in the blood . The body needs cholestrol . Cells use cholestrol to make new cell membranes and some hormones . The liver makes cholestrol for the body . Some drugs can help people with high cholestrol levels
statins : block the enzyme in the liver that is used to produce cholestrol . People will normally have to take statins for the rest of their lives . Statins can lead to muscle damage and kidney problems . Using some statins for a long time has caused high numbers of deaths
cholestrol blockers : reduce the absorption of cholestrol from the intestine into the blood . Cholestrol blockers can sometimes cause problems if the person is using other drugs
evaluate the use of two types of drug for a person with high cholestrol levels

the disadvantages of using statins rather than cholestrol blockers are statins don't cause problems if the person is using other drugs unlike cholestrol blockers

the advantages of using statins rather than cholestrol blockers is statins can damage organs but cholestrol blockers don't . Statins are for life however cholestrol blockers aren't

to conclude i think that cholestrol blocker should be used rather than statins despite the fact that statins reduce cholestrol more because statins can cause death but cholestrol blockers don't . Cholestrol blockers are also better for people with dietary cholestrol problems

most drugs that kill bacteria cannot be used to treat viral infections explain why (2)

any two from

viruses live inside cells

viruses inaccesible to dug

drug would damage body cells/tissue

antibiotic-resistant strains of bacteria are causing problems in most hospitals
explain as fully as you can , why there has been a large increase in the number of antibiotic-resistant strains of bacteria (4)

overuse of antibiotics

bacteria mutate

antibiotics kill non-resistant strains

resistant bacteria reproduce

read the description of an investigation into the link between smoking cannabis and heroin addiction
Six teenage rats where given a small dose of THC - the active chemical in cannabis - every three days between the ages of 28 and 49 days . This equivalent of human ages 12 to 18 . the amount of THC g]ven was roughly equivalent to a human smoking one cannabis joint every three days . A control group of 6 teenage rats did not recieve the THC . After 56 days catheters were inserted in all 12 of the now adult rats and they were able to self administer heroin frequently by pushin a lever . All the rats began gto self administer heroin frequently . After a while , they stabilised their dailly intake at a certain level . The ones that had been on THC as teenagers stabilised their heri intake at a much higher level than the others . They appeared to be less sensitive to the effects of heroin . This pattern continued throughout their lives . Reduced sensitivity to the heroin means that the rats take larger doses . This has been shown to increase the risk of addiction .
evaluate the investigation with respect to establishing a link between cannabis smoking and heroin addiction in humans (6)

the method in the investigation had the advantages that there was a control group used . Also the rats were the equivalent to the age of human teenagers . They controlled the amount of THC given to the rats and this was roughly equivalent to a human smoking one cannabis joint every three days . The rats were also wer allowed to choose the amount of heroin . The rats are mammals so would act in the same way as humans .

the method in the investigation had flaws because they only used a small sample size . Also the rats administers heroin in a different way to as humans would .

To conclude the rats given THC took more heroin . This is evidence for a link between cannabis and heroin . But this does not prove a link in humans

scientists are unsure whether the morning after pill may cause abnormalities among unborn Children suggest why (2)

the sample size is too small and the timescale of use is too short

some people say the morning after pill should be freely available over the counter . Give two reasons why they think this (2)

womens right of choice

it avoids later more dangerous abortion

some people think that the morning after pill should only be available on prescription suggest why they think this (2)

the possibility of side effects

the possibility that it could encourge promiscuity or irresponsible sexual behaviour , or maybe their own religious beliefs

explain in detial why a person who has been vaccianted against flu may still catch disease (6)

the flu virus mutates and WBC do not recognise mutated virus . Antibodies are ineffective against the new virus . The virus multiplies before appropriate antibodies can be formed , and the toxins released , when infected cells burst to produce flu symptoms

figure 5 shows bacteria being transfered from one petri dish , B , to another , C ,
describe fully the procedures you would use to trasnfer bacteria from dish B to dish C . Give the reason for the proceudres you describe (6)

inoculating loops are held in the flame to kill any microorganisms . The loop is cooled , so that bacteria in B are not killed when sampled . The lid of C is lifted off only slighty to transfer the bacteria to prevent contamination from the air

explain how a person becomes addicted to a drug (2)

drugs alter the chemical process in the body

and suffer withdrawal symptoms if they stop taking the drug as their body is now dependant on the drug